A. Logon to the Workstation locally as Administrator (i.e. name of machine) and goto Control Panel. Double click Network and click change. Enter the new Domain name and click OK. You will receive a message "Welcome to Domain x". Reboot the machine and you are part of the new domain.
If you wish to administer this box from the new domain you will need to add <Domain>\DomainAdmins to the local administrators group by connecting to the local user database via User Manager for Domains (i.e. \\computername)